Storing hydrogen



United States Patent 3,315,479 STORING HYDROGEN Richard H. Wiswall, Jr.,Brookhaven, and James J. Reilly,

Jr., Bellport, N.Y., assignors to the United States of America asrepresented by the United States Atomic Energy Commission No Drawing.Filed June 15, 1966, Ser. No. 558,220

4 Claims. (Cl. 62-48) ABSTRACT OF THE DISCLOSURE A method for storinghydrogen whereby gaseous hydrogen is adsorbed by nickel-magnesium alloysat temperatures above 250 C. and pressures above 18 pounds per squareinch.

. The invention described herein was made in the course of, or under acontract with the US. Atomic Energy Commission.

Prior art It is an object of this invention to provide those skilled inthe art with a simple, economical, safe method of storing hydrogen.

Description of the invention We have discovered a novel method forstoring hydrogen by forming a hydrogen metal alloy complex, whereinhydrogen gas is absorbed into a metal alloy, comprising contactinggaseous hydrogen with a solid nickel-magnesium alloy, said alloycontaining from about 40 weight percent to about 80 weight percentnickel based upon the total weight of the nickel-magnesium alloy andfrom about 20 weight to about 60 weight percent magnesium based upon thetotal weight of the nickel-magnesium alloy, while maintaining saidhydrogen and said alloy at a pressure of at least about 18 pounds persquare inch and at a temperature of at least about 250 C. until saidalloy has absorbed up to about 5 weight percent hydrogen based upon thetotal weight of the nickel-magnesium alloy. The product formed by ourmethod is a hydrogen-nickelmagnesium complex, whose exact physical andchemical structure is not known at this time.

The hydrogen-mickel-magnesiurn complexes produced by the practice of ourinvention are stable at temperatures below 250 C. and the complexes neednot be stored in pressure vessels. Thus, hydrogen can be readily storedby forming the complex in accordance with the method disclosed by ourinvention and thereafter cooling the complexes and maintaining them atnormal atmospheric pressures until it is desired to release the hydrogencontained therein. To release the hydrogen from the complex, all that isrequired to be done is to heat the hydrogen containing complex to atemperature above 250 C. and to allow the hydrogen to escape.

A unique feature of our novel complexes is the fact that hydrogen isreleased at a constant rate from a complex when the complex ismaintained at a specific temperature at or above 250 C. until thecomplex contains less than one weight percent of hydrogen based on thetotal weight of nickel-magnesium alloy contained in the complex. Forexample, a hydrogen-nickel-magnesium complex contain- 3,3 15,479Patented Apr. 25, 1967 ing 5 weight percent hydrogen based upon theweight of the nickel-magnesium alloy upon being heated at-a constanttemperature of 250 C. will maintain a constant hydrogen pressure of 18lbs. per square inch above the alloy until about one weight percent ofhydrogen remains in the complex. This feature provides those skilled inthe art with a simple hydrogen source in which the rate of release canbe carefully controlled by simply controlling the temperature of thecomplex during the release. Thus, it will be apparent to those skilledin the art that our invention can be readily adapted to conventionaltechniques to provide a safe dependable source of hydrogen for amultitude of uses such as rockets, fuel cells, etc.

In the preferred embodiment of our invention, the nickel-magnesium alloycontains 53 Weight percent nickel and 47 weight percent magnesium basedon the total weight of the alloy. The alloys found useable in ourinvention can be produced by any conventional alloying technique. Theycan be produced by simply heating the proper amounts of nickel andmagnesium under an inert or hydrogen atmosphere with an induction heateruntil a melt is formed, intimately mixing the ingredients of the meltand thereafter cooling the melt until a solid alloy is formed. Liquidmetal alloys are not desirable for use in the practice of our inventionbecause the pressure requirements required to form the desiredhydrogen-alloy complex would be too great. The presence of oxygen in thenickel-magnesium alloy is to be avoided as oxygen tends to inhibit therate of formation of the complex. We have found it preferable to use apowdered nickel-magnesium alloy in the practice of our invention becausethe increased surface area provided by the powder increases the rate ofabsorpition of the hydrogen by the alloy. However, our invention is notlimited to any particular physical shape of the alloy and blocks andmeshes of the alloy can be employed and indeed in certain applicationssuch shapes may be desirable. Conventional pressure vessels and heatingdevices may be employed in the practice of our invention.

In the preferred embodiment of our invention the hydrogen and thenickel-magnesium alloy are heated to a temperature of 300 C. andmaintained under a pressure of pounds per square inch absolute. Thepressure can be maintained by adding additional increments of hydrogento the system to counterbalance the increments taken up by the alloyduring the absorption phase of the process.

We have found that one atom of hydrogen will be adsorbed per atom ofmetal contained in the alloy. One mol of an alloy having the formula MgNi will absorb up to 4.5 mols of hydrogen during the practice of ourinvention. Thus the alloys found useable in our invention will absorbroughly 5 weight percent hydrogen based on the total alloy weight.

Example I A pparatus.-An upright reactor vessel consisting of astainless steel tube flanged on both ends and having an inside diameterof inch and a length of about 13 inches was fitted with a thermocouplewell through the top flanged end of the vessel and extended therein forabout 7 inches. A small crucible made of aluminum oxide was attached tothe bottom of the thermocuple to hold the samples to be treated at aboutthe middle of the vessel. The bottom end of the vessel was sealed and aconnection was fitted to the side of the vessel to permit gas to bewithdrawn and introduced in the vessel. The vessel was inserted into anelectrically heated furnace.

Procedure A 2 gm. sample of an alloy consisting of 45% by weight Mg and55% by weight Ni (Mg Ni) was weighed out in a dry box. The sample waspulverized so that it could through a mesh screen, reweighed andintroduced of 275 C. H was admitted to the reactor until a pres-..

sure of 125 p.s.i.a. was reached at which point the vessel was sealed.The reactor vessel was then heated to about 300 C. The rate at which thesample absorbed H could be determined by the pressure decrease in thesystem over a period of time. When absorption was essentially complete,the reactor was cooled to room temperature and gaseous H was vented fromthe system until a predeter-. mined pressure of p.s.i.a. was reached.The sample was reheated to about 300 C. and allowed to come toequilibrium and the pressure recorded. At equilibrium some gaseous H wasremoved from the system after which a new equilibrium was reached. Whenno further H evolved from the sample upon removing gaseous H the entirecycle was repeated by readimitting H into the system and reabsorbing Hin the alloy.

Results A hydrogen content of over 4 wt. percent has been repeatedlyobtained by absorption in an alloy with the starting composition of wt.percent Mg, wt. percent Ni (Mg Ni). The fact that thesorption-desorption cycle can be repeated indefinitely is of practicalsignificance for it allows for economic use of the alloys to effectuateH storage.

We have also prepared samples of the alloy which were cooled to roomtemperature afterthey had sorbed about 4 weight percent hydrogen basedupon the weight of the nickel-magnesium alloy. These samples did notlose their hydrogen upon exposure to the atmospheric conditions found inour laboratory. Further, they were not damaged when they were recycledthrough the procedure described in this example.

We claim:

1. The method of storing hydrogen comprising contacting gaseous hydrogenwith a solid nickel-magnesium alloy, said alloy being composed of fromabout 40 weight percent to about 80 weight percent nickel based on thetotal Weight of the nickel-magnesium alloy and from about 20 weightpercent to about weight percent magnesium based upon the total weight ofthe nickelmagnesium alloy, while maintaining said hydrogen and saidalloy at a pressure of at least about 18 pounds per square inch and at atemperature of at least about 250 C. until said alloy has absorbed .upto about 5 weight percent hydrogen based on the total weight of thenickel- .magnesium alloy.

References Cited by the Examiner UNITED STATES PATENTS 2,356,334 8/1944Maude et al. 6248 2,663,626 12/1953 Spangler 62-48 2,712,730 7/1955Spangler 6248 3,151,467 10/1965 Cohen et a1. 62-48 LLOYD L. KING,Primary Examiner.

1. THE METHOD OF STORING HYDROGEN COMPRISING CONTRACTING GASEOUSHYDROGEN WITH A SOLID NICKEL-MAGNESIUM ALLOY, SAID ALLOY BEING COMPOSEDOF FROM ABOUT 40 WEIGHT PERCENT TO ABOUT 80 WEIGHT PERCENT NICKEL BASEDON THE TOTAL WEIGHT OF THE NICKEL-MAGNESIUM ALLOY AND FROM ABOUT 20WEIGHT PERCENT TO ABOUT 60 WEIGHT PERCENT MAGNESIUM BASED UPON THE TOTALWEIGHT OF THE NICKELMAGNESIUM ALLOY, WHILE MAINTAINING SAID HYDROGEN ANDSAID ALLOY AT A PRESSURE OF AT LEAST ABOUT 18 POUNDS PER SQUARE INCH ANDAT A TEMPERATURE OF AT LEAST ABOUT 250* C. UNTIL SAID ALLOY HAS ABSORBEDUP TO ABOUT 5 WEIGHT PERCENT HYDROGEN BASED ON THE TOTAL WEIGHT OF THENICKELMAGNESIUM ALLOY.